Spread spectrum signal transmission method and system and also transmitter and receiver for use with the method and system

• US 5,872,806 A
• Filed: 08/09/1996
• Issued: 02/16/1999
• Est. Priority Date: 08/10/1995
• Status: Expired due to Fees

• Current Assignee: Andreas Monch, Eduard Chilla, Heinz Jurgen Frohlich, Janos Enderlein
• Original Assignee: Andreas Monch, Eduard Chilla, Heinz Jurgen Frohlich, Janos Enderlein
• Inventors: Enderlein, Janos, Monch, Andreas, Frohlich, Heinz Jurgen, Chilla, Eduard
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): Tran, Khai
• Application Number:
  US08/695,056
• Time in Patent Office: 921 Days
• Field of Search: 375/200, 375/204, 375/208, 375/201, 375/202, 375/209, 375/219, 375/220, 375/242, 364/819, 364/821, 370/342
• US Class Current: 375/130
• CPC Class Codes: H04B 1/707 using direct sequence modulation

Abstract

A spread spectrum signal transmission method and spread spectrum signal transmission system in which a carrier frequency is frequency modulated with an analog or digital baseband signal in a transmitter, the frequency modulated carrier is converted into a pulse sequence, each pulse is converted into a band-spread signal linked with a code and transmitted via an antenna, and wherein the transmitted signal is subsequently received by an antenna and linked with a code which is the time inverse of the first named code, whereby a sequence of correlation peaks arises, which are converted into a pulse sequence and subsequently frequency demodulated to obtain an output signal corresponding to the analog or digital baseband signal. The method or the system make it possible to achieve an interference-free transmission of both analog and also digital signals with low transmitter power and/or large range, with a low number of system components, i.e. with simple and cost favorable system components.

Claims

1. A spread-spectrum signal transmission method comprising:

frequency modulating a carrier frequency in a transmitter with an analog or digital baseband signal to form a frequency modulated signal;

converting the frequency modulated signal into a first pulse sequence;

trigging a first code with pulses of the first pulse sequence to thereby provide coded band-spread signals;

transmitting the coded band-spread signals via an antenna;

receiving the transmitted signals by an antenna;

decoding the received transmitted signals with a second code that is a time inverse of the first code, whereby a sequence of correlation peaks arises that is converted into a second pulse sequence; and

frequency demodulating the second pulse sequence to obtain an output signal corresponding to the analog or digital baseband signal;

wherein the conversion of the frequency modulated signal into the first pulse sequence takes place by means of a zero point detector or a threshold switch, and the first pulse sequence is supplied to a circuit in which a sequence of said coded band-spread signals is triggered by said first pulse sequence; and

wherein the decoding of the received signal with the second code is carried out by means of a correlator, an output signal of which is a sequence of correlation peaks that are converted by means of a demodulator with a threshold switch at the receiver side into said second pulse sequence, said second pulse sequence having a repetition frequency corresponding to a repetition frequency of said first pulse sequence at the transmitter side.

2. A method in accordance with claim 1, wherein a PSK transmitter filter is used to generate said coded band-spread signals in said transmitter and a PSK receiver filter containing said second code is used in said receiver to produce said sequence of correlation peaks.

3. A method in accordance with claim 1, wherein said frequency modulated signal of said transmitter is converted to a desired repetition frequency before it is used to trigger said coded-band-spread signals.

4. A method in accordance with claim 1, wherein said second pulse sequence derived from said sequence of correlation peaks comprises a reconstructed frequency modulated carrier signal, that is subjected to frequency conversion prior to demodulation.

5. A method in accordance with claim 1, wherein said coded band-spread signals in said transmitter are subjected to a frequency conversion before being applied to said antenna of said transmitter, and wherein a frequency conversion is effected at the receiver prior to the decoding with said second code.

6. A method in accordance with claim 5, wherein said sequence of correlation peaks in the receiver is reshaped after conversion by means of a demodulator with a threshold switch and subsequently by means of a pulse shaping device into a rectangular signal with transistor/transistor logic level, and is subsequently converted into a sinusoidal signal.

7. A method in accordance with claim 6, wherein said sinusoidal signal is demodulated to a receiver output signal either directly or after a frequency conversion.

8. A spread-spectrum signal transmission system comprising:

a transmitter comprising;

an oscillator for generating a carrier frequency;

a modulating device for the frequency modulating of the carrier frequency with an analog or digital baseband signal to form a frequency modulated signal;

means for converting said frequency modulated signal into a pulse sequence;

coding means for linking pulses of said pulse sequence with a first code to trigger a sequence of coded band-spread signal obtained from said coding means; and

a receiver comprising;

an antenna that supplies received signals to a decoding circuit for linking said received signals with a second code that is a time inverse of the first code of said coding means, whereby a sequence of correlation peaks arises;

a circuit for converting said sequence of correlation peaks into a sinusoidal signal; and

a demodulator for demodulating said sinusoidal signal into an output signal corresponding to said analog or digital baseband signal;

wherein said means for converting said frequency modulated signal into the pulse sequence includes a zero point detector or a threshold switch and said coding means for linking pulses of said pulse sequence with the first code comprises a PSK transmission filter, and wherein said decoding circuit of said receiver has a PSK receiving filter containing the time inverse code of the first code of said coding means, wherein said sequence of correlation peaks are obtained at an output of said PSK receiving filter, and said decoding circuit includes a demodulator having a threshold switch and a pulse shaping device, and wherein said decoding circuit further includes a signal shaping device having an output at which a modulated signal is available.

9. A spread-spectrum signal transmission system in accordance with claim 8, wherein said transmitter has a frequency converter for converting said frequency modulated signal to a desired repetition frequency prior to passing it to said coding means.

10. A spread-spectrum signal transmission system in accordance with claim 9, wherein a band pass filter and an amplifier are provided in the transmitter between said modulation device and said frequency converter.

11. A spread-spectrum signal transmission system in accordance with claim 8, wherein said receiver has a frequency converter between said antenna and said decoding circuit.

12. A spread-spectrum signal transmission system in accordance with claim 8, wherein said transmitter has a frequency converter provided between said coding means and said antenna circuit.

13. A spread-spectrum signal transmission system in accordance with claim 8, wherein said receiver has a pulse shaping device that reshapes said sequence of correlation peaks after the conversion by means of a demodulator with a threshold switch into a rectangular signal with transistor/transistor logic level and wherein a pulse shaping device is provided to convert said rectangular signal into a sinusoidal signal.

14. A spread-spectrum signal transmission system in accordance with claim 13, wherein said transmitter contains an amplifier to amplify said baseband signal and a filter to filter the amplified baseband signal.

15. A spread-spectrum signal transmission system in accordance with claim 13, wherein said pulse shaping device of said receiver contains a monostable multivibrator that generates a pulse for each correlation peak and falls back to an output value after expiration of a holding time, and wherein said holding time is shorter than the time spacing between two sequential pulses at a highest provided repetition frequency.

16. A spread-spectrum signal transmission system in accordance with claim 15, wherein said rectangular signal is passed to an integrator to effect frequency demodulation by integration of the rectangular signal over time.

17. A spaced-spectrum signal transmission system comprising:

a transmitter comprising;

an oscillator for generating a carrier frequency;

a modulation device for the frequency modulation of the carrier frequency with an analog or digital baseband signal to form a frequency modulated signal; and

means for converting said frequency modulated signal into a pulse sequence and coding means for linking pulses of said pulse sequence with a first code to trigger a sequence of coded band-spread signals obtained from said coding means; and

a receiver comprising;

an antenna that supplies received signals to a decoding circuit for linking said received signals with a second code that is a time inverse code of the first code of said coding means, whereby a sequence of correlation peaks arises;

a circuit for converting said sequence of correlation peaks into a sinusoidal signal; and

a demodulator for demodulating said sinusoidal signal into an output signal corresponding to said analog or digital baseband signal;

wherein said pulse shaping device of said receiver contains a monostable multivibrator that generates a pulse for each correlation peak and falls back to an output value after expiration of a holding time, with said holding time being shorter than the time spacing between two sequential pulses at a highest provided repetition frequency.

18. A spread-spectrum signal transmission system in accordance with claim 17, wherein side rectangular signal is passed to an integrator to effect frequency demodulation by integration of the rectangular signal over time.

19. A spread-spectrum signal transmission system comprising:

a transmitter comprising;

an oscillator for generating a carrier frequency;

a modulation device for a frequency modulation of the carrier frequency with an analog or digital baseband signal to form a frequency modulated signal;

means for converting said frequency modulated signal into a simplified pulse sequence representing a repeating feature of said frequency-modulated signal; and

coding means for linking pulses of said simplified pulse sequence with a first code to trigger the transmission of a sequence of predetermined, substantially identical, coded band-spread signals obtained from said coding means;

a receiver comprising;

an antenna that supplies received signals to a decoding circuit for linking said received signals with a second code being a time inverse code of the first code of said coding means, whereby a sequence of correlation peaks arises, corresponding to said simplified pulse sequence;

a circuit for converting said sequence of correlation peaks into a sinusoidal signal; and

a demodulator for demodulating said sinusoidal signal into an output signal corresponding to said analog or digital baseband signal.